This invention relates in general to Electronic Control Units for controlling a vehicle brake system and in particular to integration of vehicle motion sensors into an Electronic Control Unit.
Many vehicles being currently produced by automotive manufacturers include automatic brake control systems that are integrated with their hydraulic brake systems. Such systems include Anti-lock Brake Systems (ABS) that prevent wheel lock-up during braking cycles, Vehicle Stability Control (VSC) systems that assist in preventing loss of directional control of a vehicle during vehicle maneuvers and Traction Control (TC) systems to prevent slippage of driven wheels on low mu surfaces, as encountered with icy road surfaces. Additionally, such systems also assist in preventing loss of directional control when the vehicle is operated upon normal or even high mu surfaces, as can occur during accident avoidance maneuvers.
An automatic brake control system typically includes an electro-hydraulic control unit that is integrated with the brake lines of the hydraulic brake system.
Referring now to the drawings, there is shown in FIG. 1, a typical electro-hydraulic control unit 10 for an automatic brake control system. The electro-hydraulic control unit 10 typically includes an Electronic Control Unit (ECU) 12 which is mounted upon a hydraulic valve body 14. The hydraulic valve body 14 is connected to the vehicle hydraulic brake system. The ECU 12 includes a microprocessor and control algorithm for operating the brake system. A plurality of solenoid valves are disposed within the hydraulic valve body 14. The solenoid valves can include normally open isolation valves and normally closed dump valves. The ECU 12 is connected to the solenoid valve coils and one or more wheel speed sensors (not shown). A pump 16 also is mounted upon the hydraulic valve body 14 to supply pressurized brake fluid to the brake control system. The operation of the pump is controlled by the ECU microprocessor.
Typically, the ECU 12 is removable from the hydraulic valve body 14 to allow servicing of the unit. Usually, a faulty ECU 12 will be simply swapped for an operational unit to allow the vehicle to be quickly returned to service. The faulty ECU can then be either repaired at the service facility or returned to the manufacturer. Accordingly, the solenoid valve coils that are connected to the ECU 12 are removable with the ECU from the solenoid valves disposed within the hydraulic valve body 14. The valves and hydraulic valve body 14 form a sealed hydraulic system with the vehicle brake system so that it is not necessary to bleed the vehicle brakes following removal and replacement of the ECU 12.
During vehicle operation, the ECU microprocessor continuously receives speed signals from the wheel speed sensors. When the microprocessor senses an impending vehicle control problem, the brake control system is activated. The ECU microprocessor starts the pump to supply pressurized brake fluid and causes the solenoid valves to cyclically apply and relieve hydraulic pressure to the wheel brakes to improve vehicle stability control.
The brake control system also can include motion sensors that supply vehicle motion data to the microprocessor. The motion sensors can include one or more acceleration sensors for measuring acceleration and/or deceleration of the vehicle. The acceleration is usually sensed relative to one or more of three orthogonal vehicle reference axes, which are commonly referred to the lateral, transverse and vertical axes. The motion sensors also can include one or more angular rate, or gyroscopic, sensors, that measure vehicle yaw, roll or pitch about the vehicle's reference axes.